I am at something of a crossroads in my photographic journey, as I have been getting more interested in photography as a hobby and am looking for some insight from others who have been involved in the hobby (or profession for some) much longer than I have.

About a year ago I purchased a Sony Nex 6 with a kit lens (16-50pz) and tele-zoom (55-210). I later purchased a few other lenses, the most expensive (and best of them) is the SEL 35/1.8. Previously I had been using an advanced P&S and bridge camera.

I would like to replace the NEX kit lens with something faster and preferably a little longer. The newish Zeiss 16-70 is the obvious choice, but at $1000 it is quite an investment. Add to that the fact that Sony is now spending most of its efforts on its full frame cameras and I start to wonder whether I should jump now to a different system that will provide the most flexibility for me to grow.

A Canon or Nikon DSLR is certainly a "mature" system, but I think I would want to stay on the smaller and lighter side, which means beginner bodies that may not be on par feature-wise as the NEX 6 I already have (is that right?).

Another option is m4/3, which also has many more native lens choices than Sony (I'm not including adapted manual lenses, of course), but a smaller sensor (although I'm not sure how much of a real world difference there would be).

Finally, I could just keep the NEX 6 and not worry about what "may" be. It may be that I will never really feel the need for anything more than is already available in the Sony NEX system. Or perhaps when and if I do, there will be something else that looks like the obvious choice.

I guess I'm just a little leery of investing heavily in a system that I may find a need to move away from.

The NEX-6 is a fine camera, but for the same price, other cameras often offer more, and the associated lenses are often better and cheaper.

It seems you've already made a significant investment in Sony's E-Mount lenses, so switching to a different system may be costly, in terms of what you'd be leaving behind.

If all your looking for is better kit lens with a greater zoom range, you might consider the Sony E PZ 18-105mm F4 G OSS ($600.) It seems to be very sharp throughout its zoom range, though it does seem to have problems with flare, and the distortion on the long end seems to be heavy. In addition, it's a big, heavy lens. But reports are that it is a much better lens than the kit lens you're using now.

Would a lens like that help you to be more satisfied with your NEX, or would you still be looking for a replacement?

Given that you say you've invested in "other lenses" in addition to the ones listed- jumping ship to another system/format/brand would seem on the face of it an expensive proposition- probably more expensive than the Zeiss 16-70 you mention..!
Given also that the NEX-6 is a very capable camera in many departments, is there something you feel you're missing...?

For now anyway what I feel I am missing is a good all around zoom for travel and day-to-day use. So a replacement for the kit lens would satisfy me for the moment although I'm not sure if the 18-105 would necessarily do it. I have shied away from the 18-105 because in addition to being fairly large for an every day walk-around lens it is a power zoom, and that is one of my complaints about the 16-50. I have heard, however, that the 18-105 isn't quite as big of a pain because it doesn't retract, so perhaps it is worth at least looking at.

As far as my investment, it is true that I would take something of a financial hit if I were to switch to a different system now. The lenses I have were purchased at pretty good prices, so I could probably get a reasonable amount of my money out of them (Just so you know what I'm talking about, in addition to the 16-50 and 55-210 purchased as an initial kit, I have a 19mm/2.8 Sigma, SEL 16mm F2.8 with the ultra wide adapter and the SEL 35 F1.8). The initial kit is probably a different story. Even though I bought the NEX 6 after its price had come down some from its launch price, it has still come down in price a good bit more since then with the introduction of the A6000.

If I had to guess, I figure I would probably be looking at about a $600-$800 loss in my investment, but of course I did get the use of the camera for about a year.

It IS a very capable camera and I am generally pretty happy with it (of course there are things I can complain about, but the same is true with any camera). I suppose my fear is that I'll add another $600- $1000 to my current investment, be satisfied now, and then a year from now or so, I'll find there is some other lens that I could really use that the Sony platform doesn't have or that is priced very expensively given its quality (maybe a good macro lens or a faster tele-zoom, etc.) Of course, that day might not come and at that point I will have had the use of the camera for that much longer. Also the lenses tend to hold their value much better than the camera so presumably whatever I add in that department won't depreciate quite as fast.

One follow up wrinkle. I have just started trying to take some action shots of very fast pets (often jumping) in less than ideal lighting. Would I need a DSLR for this or is a mirrorless camera up to the task? It's not clear to me whether I would need a faster auto focus system or if getting a good result is really primarily dependent on my own technique/practice, which can always be improved.

In less than ideal lighting I'd suggest the phase detection AF system of a DSLR as opposed to a contrast detect AF of a mirrorless cam' would be superior in your suggested scenario- though not all DSLR's are equal...
Of course, a fast lens would help in both cases- and some mirrorless cam's have hybrid AF systems, improving things somewhat...
You say you've been "trying" these type of shots...
Was this with your Sony...? Was it successful..?

Yes, with the Sony, which as you know does have a hybrid auto focus, but not up to the standards that the new A6000 is supposed to have. And the results were marginal. Part of the problem was probably too slow of a shutter speed causing some blur. But another part of the issue seemed to be that the auto focus didn't lock in precisely (or it locked in on something other than the subject - like the wall behind it).

Trying to find an appropriate combination of ISO, aperture and shutter speed is a trial and error thing, obviously. And when the light is less than full bright daylight (this was in shade on a screened porch that isn't in full sun) it makes things a little difficult.

Clearly I need some practice. I'm just not certain how much is me and how much is the auto focus system. I did try a 50/1.7 manual lens, but the results were about the same. Predicting the location of the action was extremely difficult, so it was just a matter of luck as to whether it would occur where I pre-focused.

Your 55-210 lens is probably the best for what you want to do, and your NEX-6 is probably the best camera for what you want to do. Sony's hybrid AF uses the phase detection sensors to get close and contrast detection AF to get it right, but even that can miss moving subjects.

If you want to keep your E-Mount lenses, I'd say you should get something like the A6000. The problem with that is that the 55-210 is the longest E-Mount lens, and that's probably not long enough. When I'm shooting fast moving pets (equestrian sports), I find that 300mm is good; for dogs you should probably have something longer than the 55-210 you're using now. I use A (Aperture Priority), open the lens to its largest aperture, and use an ISO that will keep the shutter speed over 1/250 at least. When shooting indoors, you'll probably be shooting at ISOs high enough to get significant image noise. A lens with a large aperture can help, but if you give up focal length to get it, you're going to have trouble with composition. You need to keep the subject in as many of the PDAF sensors as possible.

Are the pets jumping fixed obstacles, as in dog shows, or training for such? If so, you need to manually focus on where the subject is going to be when you take the shot, not depend on the camera to try to catch a moving subject. Also, positioning yourself so the subject is moving across the field of vision, rather than towards or away from you helps. If possible, use a shoe mount or external flash, which will stop motion well, and allow you to use smaller apertures, to help keep pictures sharp even with slight mis-focus. If you can't use flash, go with a high enough ISO setting, as TCav mentions.
BTW, the pic for my avatar was taken with an all manual 35mm film camera.
brian